Signup Usermeta in Single User Environment Issues

I’m working on a plugin that grabs some dynamically generated fields on the user registration page (these fields don’t exist in xprofile) and adds them to the user’s meta information. I’ve got it work in a multisite environment (MU 2.9.2 + BuddyPress 1.2.5.2) with the code below:

That code adds the info the meta section in wp_signups just fine. I can’t get it to work in a single user environment (WordPress 2.9.2 + BuddyPress 1.2.5.2). The array of data from the fields doesn’t show up in wp_usermeta. Any thoughts?

UPDATE: It looks like $usermeta is getting the string that should go in ‘meta_key’ and the array of data that would go in ‘meta_value’, but it is not actually doing the insert. Is this something goofy with a validation against xprofile fields?